JPH11161935A - Magnetic recording media - Google Patents

Abstract

(57) [Problem] To provide a metal thin film type magnetic recording medium which shows excellent durability and does not cause clogging of a magnetic head. A magnetic recording medium comprising a support, a metal magnetic layer formed on the support, and a lubricating layer formed on the metal magnetic layer, wherein at least one surface of the medium has:
A magnetic recording medium having a large number of minute grooves for holding a lubricant at a specific ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic recording medium. More specifically, the present invention relates to a magnetic recording medium having a lubricating layer formed on a metal thin film layer.

[0002]

2. Description of the Related Art A so-called metal thin film type magnetic recording medium in which a metal is deposited on a support in a vacuum in a vacuum or the like can increase the density of the magnetic material because the magnetic layer contains no binder at all. Is promising for high-density recording. However, the magnetic layer of the metal thin-film type magnetic recording medium has only a metal adhered to the support, and as such, has poor corrosion resistance and durability. In order to improve this, a fluorine-based material such as perfluoropolyether is used. To form a lubricating layer by applying a lubricant, a hydrocarbon-based lubricant or a lubricant using them in combination.

[0003]

However, since the magnetic layer surface of the metal thin film type magnetic recording medium is a continuous flat surface, and a fluid lubricant is generally used, the lubricating metal thin film type magnetic recording medium is generally used. The transfer or detachment of the agent occurs, and as a result, the durability may be reduced or the magnetic head may be clogged.

[0004]

Means for Solving the Problems The inventors of the present invention have intensively studied to obtain a metal thin film type magnetic recording medium which does not move or desorb lubricant, has excellent durability, and does not cause clogging of a magnetic head. As a result, on at least one surface of the magnetic recording medium, it was found that by forming a large number of fine crack-shaped grooves capable of holding a lubricant, the intended magnetic recording medium was obtained, and to complete the present invention. Reached.

That is, the present invention relates to a magnetic recording medium having a support, at least one metal magnetic layer formed on the support, and a lubricating layer formed on the magnetic layer. At least one surface of the medium has a large number of fine crack-shaped grooves capable of holding a lubricant forming the lubricating layer, and the size of the grooves is 5 to 50 nm in width and 10 to 600 in length.
nm and the number is 1200 nm × 880 in the unit field of view.
It is intended to provide a magnetic recording medium characterized in that the number is 10 to 80 per nm.

[0006] The magnetic recording medium according to the present invention,
Many fine grooves that can hold the lubricant can be confirmed by observation with a scanning electron microscope (SEM).
FIG. 1 shows an SEM photograph of the surface on the magnetic layer side of the magnetic recording medium of the present invention obtained in Example 1 described later. As is clear from FIG. 1, a large number of minute grooves are present in the medium surface in the form of cracks. In the magnetic recording medium of the present invention, since the lubricant can be held in the groove, it is considered that movement and detachment of the lubricant are suppressed.

In order to obtain excellent effects of durability and prevention of clogging, among these fine grooves, grooves having a width of 5 to 50 nm and a length of 10 to 600 nm are observed by a SEM to have a unit field of view of 1200 nm × 880 nm. It is necessary to be present at a ratio of 10 to 80 pieces. As shown in FIG. 1, the shape of this groove is indefinite, but the main shape is extracted and shown in FIG. As shown in FIG. 4, the shapes of these grooves are roughly classified into an I-shape (FIG. 4a), a U-shape (FIG. 4b),
The shape is an S-shape (FIG. 4c), and these shapes are continuously connected. The length of the groove in the present invention is the length in the linear direction (L in FIG. 4A) in the case of the I-shape, and the longest linear length (L in FIG. 4B) in the U-shape. In a shape in which a plurality of molds are continuously connected, the length is a length when approximated to a straight line (L in FIG. 4C). The width of the groove refers to the maximum width of the groove (W in FIGS. 4A to 4C).

The groove has a width of 5 to 50 nm and a length of 10 to 10 nm.
Smaller than 600 nm, and the number of
If the ratio is less than 10 to 80 lines per 00 nm × 880 nm, the amount of the lubricant that can be retained is small, and the effects of durability and prevention of clogging are not exhibited. Conversely, the size of the groove is larger than 5 to 50 nm in width and 10 to 600 nm in length, and the number of grooves is 1200 nm × 880 n in a unit field of view.
If the ratio is more than 10 to 80 per m, the film becomes brittle in terms of strength, and the durability deteriorates. The depth of such a groove is determined by the film thickness, but is about 2 to 30 nm.

In order to form minute grooves on the medium surface at a specific ratio, conditions for forming the metal magnetic layer are adjusted. More specifically, the magnetic recording medium of the present invention can be obtained by adjusting the conditions when forming a metal thin film type magnetic layer by the vacuum oblique deposition method using an apparatus as shown in FIG.

In FIG. 3, 1 is a support, 2 is a can roll, 3a is an unwind roll, 3b is a take-up roll, 4 crucibles, 5 is a ferromagnetic metal, 6 is an electron gun, 7 is an adhesion plate, 8 Is a gas nozzle, 9 is a bombard apparatus, and 10 is a vacuum chamber. Here, a crucible 4 having high heat resistance such as alumina or magnesium oxide is used. In addition, crucible 4
Examples of the ferromagnetic metal 5 accommodated in
o, Ni and other metals, Co-Ni alloys, Co-P
t-based alloy, Co-Ni-Pt-based alloy, Fe-Co-based alloy, Fe-Ni-based alloy, Fe-Co-Ni-based alloy, Fe
-Co-B-based alloy, Co-Ni-Fe-B-based alloy, Co
-Cr-based alloys or alloys containing a metal such as Al are used. Further, these oxides, nitrides, carbides and the like are also used. An oxidizing gas may be supplied during the formation of the metal thin film to oxidize the surface of the metal thin film. However, it is necessary to pay attention to the surface state of the magnetic layer, which affects the surface state of the final product. . Also. The magnetic layer may be composed of one metal thin film or may be composed of two or more metal thin films. The magnetic layer is 2
When it is composed of more than two layers of metal thin films, the material of each metal thin film may be the same or different. The magnetic layer generally has a thickness of 50 to 500 nm.
It is preferred that

The unwinding roll 3a is provided in the vacuum chamber 10.
And the take-up roll 3b are provided, and the support 1 is wound around the lower surface of the can roll 2 to travel while being unwound from the unwind roll 3a and wound up by the take-up roll 3b. ing. A crucible 4 is placed below the can roll 2, and a ferromagnetic metal 5 is accommodated therein. The ferromagnetic metal 5 is irradiated by bending an electron beam from an electron gun 6,
Thereby, the ferromagnetic metal 5 is heated and evaporated. Then, by introducing an oxygen gas or the like from the gas nozzle 8 into the deposition region as needed, a oxidized column structure of the metal thin film can be formed.

In the above, a magnetic recording medium having a groove defined in the present invention can be obtained by appropriately combining the following conditions at the time of vapor deposition.・ Maximum incidence angle: 80 to 84 ° ・ Minimum incidence angle: 53 to 57 ° ・ Exhaust vacuum degree: 1.2 × 10 ^{-5 to} 2.8 × 10 ^-6 Torr
r ・ Electron gun output: 100-300 kW ・ Oxygen gas supply: 800-1000 SCCM ・ Support running speed: 30-50 m / min ・ Can roll diameter: 40-60 cm ・ Can roll surface roughness: 0.05-0. 1S ・ Can roll temperature: -60 to -30 ° C. ・ Tension of support: 1.0 to 2.0 kg / 155 mm ・ Hanging angle to can roll: 260 to 280 ° ・ Bombard gas: oxygen, nitrogen ・ Bombard voltage: 350 -450 V-Bombard current: 350-450 mA.

In particular, the number of grooves is set to a unit field of view of 1200 nm × 8.
In order to control between 10 and 80 lines per 80 nm, among the above parameters, the electron gun output, the accompanying gas flow rate, and the can roll temperature (base temperature) are appropriately adjusted. Specifically, in the above range, if the output of the electron gun is increased, the gas flow rate is increased, and the base temperature is lowered, the number of grooves increases. It is desirable that all of the above parameters are within the above ranges in terms of controlling the number and size of the grooves.

In the magnetic recording medium of the present invention, a protective layer can be provided on the above magnetic layer. In this case, the protective layer is generally made of carbon or carbide, nitride or oxide, especially diamond-like carbon, diamond, boron carbide, silicon carbide, boron nitride, silicon nitride, silicon oxide, chromium oxide or oxide in vacuum. It is preferably formed by forming a film of aluminum or the like. As the protective layer, it is particularly preferable to use a carbon thin film layer in an amorphous state, a graphite state, a diamond state, or a mixed state or a laminated state thereof. Although the thickness of the protective layer is not particularly limited, a general thickness of 3
It is preferably about 30 nm. When the thickness is in this range, the protective layer is formed according to the unevenness reflecting the groove on the magnetic layer. That is, it does not affect the shape and number of grooves on the magnetic layer. As a method for forming the protective layer, a plasma deposition method, particularly a plasma CVD method, is preferable. In particular, ECR (Electron Cyclotron Resonanc) using microwaves
e) The method using radio frequency (RF) is effective.
When the protective layer is formed by the CVD method, any of gaseous, liquid and solid materials may be used.

Further, the magnetic recording medium of the present invention has a lubricating layer on the metal magnetic layer. Such a lubricating layer may be formed in a thin film directly on the magnetic layer, or may be formed in a thin film on a protective layer or the like provided on the magnetic layer. As the lubricant for forming the lubricating layer, it is preferable to use a fluorine-based lubricant. As the fluorine-based lubricant, for example, HOOC-CF ₂ (OC ₂ F ₄ ) _p (OCF ₂ ) _q -OCF ₂ COOH, F- (CF ₂ CF ₂ CF
Carboxyl-modified perfluoropolyether such as ₂ O) _n -CF ₂ CF ₂ COOH, HOCH ₂ -CF ₂ (OC ₂ F ₄ ) _p (OCF ₂ ) _q -OCF ₂ -CH ₂
Alcohol-modified perfluoropolyethers such as OH, and one or some of the molecules have a saturated hydrocarbon group such as an alkyl group, or an unsaturated hydrocarbon group, an aromatic hydrocarbon group, or another functional group. And the like. Specifically, the brand name FO of Montecatini
MBLIN Z DIAC and trade name FOMBLIN Z
DOL, Daikin Industries' trade name Demnum SA, and the like. These fluorine-based lubricants have a molecular weight of 500 to 500.
00, particularly preferably 500 to 4000.

The lubricating layer may be formed by dissolving a fluorine-based lubricant in a solvent and applying the lubricant in the air, or by spraying a lubricant. Particularly, a method of spraying in a vacuum is preferable. In the method of spraying a lubricant in a vacuum, the fluorine-based lubricant is preferably sprayed onto a magnetic layer formed on a support by a sprayer equipped with an ultrasonic oscillator (hereinafter referred to as an ultrasonic sprayer). More specifically, the ultrasonic sprayer includes a lubricant supply unit, and a unit that applies ultrasonic waves to the lubricant supplied from the lubricant unit to atomize the lubricant (ultrasonic oscillator).
And a nozzle for spraying the atomized lubricant. Further, a nozzle type spraying device may be used. As the nozzle type spraying device, a device generally called a one-fluid nozzle can be used. By spraying the lubricant as fine particles using an ultrasonic atomizer, it is weak at high temperatures (200 ° C. or higher) and has a low vapor pressure. It is possible to spray a fluorine-based lubricant such as fluoropolyether in a vacuum.

In spraying the lubricant, the lubricant is sprayed with a fluorinated inert solvent (for example, perfluorocarbon such as "Fluorinert" manufactured by Sumitomo 3M Ltd.) or perfluoropolyether such as "Galden" manufactured by Montecatini Co., Ltd. ), And is preferably used as a solution dissolved in an appropriate solvent such as an alcohol solvent. In that case, the lubricant concentration is usually 0.01 to 0.2% by weight or 0.3 to
3.0% by weight.

In the magnetic recording medium of the present invention, other layers can be provided as necessary in addition to the above protective layer. For example, an undercoat layer may be provided between the support and the magnetic layer to improve the adhesion between the two, or a surface of the support opposite to the surface on which the magnetic layer is formed. In addition, a back coat layer for improving running properties and durability of the magnetic recording medium can be provided.
In this case, the back coat layer may be any of a coating type and a metal thin film type. Examples of the coating type back coat layer include a known back coat layer containing carbon black or the like and a binder as main components. The metal thin film type back coat layer is generally made of Al, Cu, Si, Fe, Mo, Mn.
Alternatively, it is formed by forming a film of Zn or the like, or an alloy, an oxide, a nitride, a carbide, or the like thereof by a vacuum film formation method. The thickness of the back coat layer is generally 50 to 100.
It is preferably 0 nm. In the present invention,
The above groove may be present on the surface on the side where the back coat layer is formed. In this case, the back coat layer is a metal thin film type back coat layer, and a lubricating layer is formed on the back coat layer in the same manner as described above.

As a support for the magnetic recording medium of the present invention, a known non-magnetic support can be used without any particular limitation. Specifically, known resins such as polyethylene terephthalate, polyethylene naphthalate, polyphenylene sulfide, polycarbonate, polyamide, polyimide, polyamide imide, polysulfone, aramid, and aromatic polyamide; metals such as aluminum and copper; paper and the like are used. be able to. The form may be any of a film, tape, sheet, disk, drum and the like. Before providing the magnetic layer on the support, the surface thereof may be subjected to corona discharge treatment, plasma treatment, easy adhesion treatment, heat treatment, dust removal treatment, bombardment treatment, or the like in the air and / or in vacuum. The preferred thickness of the support is 1 to 300 μm.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 (1) Production of Magnetic Tape A magnetic layer made of Co was formed on a 6 μm-thick PET film by vacuum oblique deposition using the apparatus shown in FIG. 12 μm).

Maximum incident angle: 82 ° Minimum incident angle: 55 ° Exhaust vacuum: 6.2 × 10 ^-6 Torr Electron gun output: 100 kW Oxygen gas supply: 800 SCCM Support traveling speed: 30 m / Min. Crucible: crucible made of alumina-Can roll diameter: 50 cm-Can roll surface roughness: 0.1 S-Can roll temperature: -30 ° C-Support tension: 1.5 kg / 155 mm-Dangle to can roll: 280 ° Bombard gas: oxygen gas Bombard gas flow rate: 40 SCCM Bombard voltage: 400 V Bombard current: 200 mA.

Next, on this magnetic layer, ECR plasma C
According to the VD method, a benzene flow rate of 6
0SCCM, 800W microwave power, thickness 1
A protective layer made of 0 nm DLC (diamond-like carbon) was formed. A back coat layer made of carbon black and a binder was formed to a thickness of 0.5 μm on the surface of the PET film opposite to the surface on which the magnetic layer was formed. Next, on the protective layer, a fluorine-based lubricant (manufactured by Montecatini Co., trade name: FOMBLIN Z DOL)
A lubricating layer having a thickness of 2 nm was formed.

The Co-based magnetic layer, DL,
The film on which the C protective layer, the fluorine-based lubricating layer and the back coat layer were formed was cut into a width of 8 mm, and was loaded into a cassette case to obtain an 8 mm video tape.

(2) Performance Evaluation The 8 mm video tape obtained above was evaluated for still durability and head clogging by the following methods.
Table 1 shows the results.

<SEM Observation> The surface of the 8 mm video tape on which the magnetic layer is formed is observed by SEM (magnification 100,000) to obtain a unit visual field of 1200 nm × 880 nm.
The number of grooves having a width of 5 to 50 nm and a length of 10 to 600 nm was counted. FIG. 1 shows an SEM photograph at that time.

<Still Durability> The still durability was determined by using a commercially available 8 mm VTR (model EV-S900, manufactured by Sony Corporation) and measuring the time required for the output to decrease by 3 dB from the initial value.

<Presence / absence of head clogging> After the still durability test, the wet cleaning tape is run. If the output recovers, it is determined that “head clogging has occurred”, and if the output has not recovered, “head clogging has not occurred”.

Example 2 In Example 1, the output of the electron gun was 200 kW, the supply amount of oxygen gas was 900 SCCM, and the traveling speed of the support was 40 m / m.
An 8 mm video tape was produced in the same manner as in Example 1 except that the support tension was changed to 1.7 kg / 155 mm, and the same evaluation was performed. Table 1 shows the results.

Example 3 In Example 1, the output of the electron gun was 300 kW, the supply amount of oxygen gas was 1000 SCCM, and the running speed of the support was 50 m / m.
An 8 mm video tape was prepared and evaluated in the same manner as in Example 1 except that the support tension was 2.0 kg / 155 mm and the can roll temperature was −60 ° C. Table 1 shows the results.

Comparative Example 1 In Example 1, the output of the electron gun was 30 kW, the supply amount of oxygen gas was 400 SCCM, the running speed of the support was 10 m / min,
The crucible is a copper crucible (cooling circulation), the support tension is 2.0 kg / 155 mm, and the can roll temperature is −60 ° C.
An 8 mm video tape was prepared and evaluated in the same manner as in Example 1 except that the above conditions were satisfied. Table 1 shows the results. FIG. 2 shows an SEM photograph of the surface of the 8 mm video tape on the side where the magnetic layer is formed, but no fine crack-shaped grooves are observed in this tape.

Comparative Example 2 In Example 1, the output of the electron gun was 80 kW, the supply amount of oxygen gas was 600 SCCM, the traveling speed of the support was 20 m / min,
An 8 mm video tape was prepared and evaluated in the same manner as in Example 1 except that the crucible was a copper crucible (cooling circulation), the support tension was 2.0 kg / 155 mm, and the can roll temperature was 20 ° C. . Table 1 shows the results.

Comparative Example 3 In Example 1, the output of the electron gun was 500 kW, the supply amount of oxygen gas was 1200 SCCM, and the traveling speed of the support was 65 m / m.
An 8 mm video tape was produced in the same manner as in Example 1 except that the support tension was changed to 2.2 kg / 155 mm, and the same evaluation was performed. Table 1 shows the results.

[0034]

[Table 1]

[0035]

According to the present invention, it is possible to obtain a metal thin-film type magnetic recording medium having remarkably improved durability and no head clogging.

[Brief description of the drawings]

FIG. 1 is an SE showing a surface state of a magnetic recording medium of Example 1.
It is an M photograph.

FIG. 2 shows SE showing the surface state of a magnetic recording medium of Comparative Example 1.
It is an M photograph.

FIG. 3 is a schematic view showing an example of an apparatus for manufacturing a magnetic recording medium of the present invention.

FIG. 4 is a schematic view showing the shape and size of a groove.

[Explanation of symbols]

 1: support 2: cooling can roll 4: crucible 6: electron gun

Continuing on the front page (72) Inventor Toshio Yamazaki 2606 Akabane, Kakaicho, Haga-gun, Tochigi Pref.

Claims (3)

[Claims] 1. A magnetic recording medium comprising: a support; at least one metallic magnetic layer formed on the support; and a lubricating layer formed on the magnetic layer. On one surface, there are a large number of fine crack-shaped grooves capable of holding the lubricant forming the lubricating layer, the size of the grooves is 5 to 50 nm in width and 10 to 600 nm in length, and the number is a unit. 10-8 per 1200nm x 880nm field of view
A magnetic recording medium, wherein the number is zero. 2. The magnetic recording medium according to claim 1, wherein a protective layer made of carbon is formed on the metal magnetic layer. 3. The magnetic recording medium according to claim 2, wherein said metal magnetic layer is formed by an evaporation method, and said protective layer is formed by a plasma evaporation method.